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Error code reference

Bosch Washer Error Code dr:18

Peak voltage too high

Bosch codesBosch washer codes

Peak voltage too high — faulty motor control.

First step from the service manual

Run test P4; replace faulty motor control.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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  • Wiring diagram references and connector pinouts from the OEM service manual
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What dr:18 means on a Bosch washer

The dr:18 error code on a Bosch washer indicates that the motor control board has detected a peak voltage level that exceeds the acceptable threshold during motor operation. The motor control unit (MCU) continuously monitors voltage levels supplied to and generated by the drive motor. When peak voltage spikes beyond the designed operating limits, the MCU registers this fault and halts operation to protect downstream components from damage.

The motor control board is responsible for regulating power delivery to the wash motor, converting incoming AC power to controlled DC output, and managing motor speed and torque throughout each cycle. A peak voltage fault of this type is typically caused by a failing or failed motor control board that can no longer regulate voltage properly. Internal component degradation within the MCU, such as failing capacitors or damaged transistors on the control board, can cause uncontrolled voltage spikes that trigger this code.

To confirm the fault, the diagnostic procedure begins with test P4, which is the designated motor control test sequence for this platform. This test exercises the motor control circuitry and confirms whether the voltage irregularity originates from the board itself. If test P4 reproduces or confirms the fault, the motor control board requires replacement. In some cases, wiring harness issues between the control board and motor can contribute to abnormal voltage readings, so inspecting the harness connections before condemning the board is a worthwhile step.

Source: manufacturer service documentation.

Common causes of dr:18

  1. 01

    Failed motor control board

    Part replacement

    The motor control board is the primary suspect for dr:18. Internal component failure causes the board to generate or allow voltage spikes beyond acceptable peak limits, triggering the fault code.

  2. 02

    Degraded capacitors on the MCU

    Part replacement

    Capacitors within the motor control unit can degrade over time, reducing their ability to smooth and regulate voltage. This leads to peak voltage spikes that exceed the board's fault threshold.

  3. 03

    Wiring harness fault between MCU and motor

    Wiring / connection

    Damaged, corroded, or loose wiring connections between the motor control board and the drive motor can produce erratic voltage readings. Inspect the harness connectors at both ends for damage or poor seating before replacing the board.

  4. 04

    Drive motor winding fault

    Part replacement

    A partially shorted or failing motor winding can create back-EMF spikes that register as peak overvoltage at the control board. This can be checked by measuring motor winding resistance and comparing to specification.

See the test procedure for each cause

Frequently asked questions about dr:18

What does dr:18 mean on a Bosch washer?
The dr:18 code means the motor control system detected a peak voltage level that was too high during operation. This points to a fault within the motor control board, which regulates power delivery to the drive motor. The machine shuts down when this condition is detected to prevent further electrical damage. Diagnostic test P4 is used to confirm the fault before any parts are replaced.
Can I fix dr:18 on my Bosch washer myself?
Diagnosing and repairing dr:18 requires running test P4 in the washer's service diagnostic mode, which involves accessing internal components and understanding the results. If you are comfortable working with appliance electronics and can safely access the motor control board, inspecting wiring connections is a reasonable starting point. However, replacing the motor control board itself is a moderately advanced repair and involves handling high-voltage components, so many owners choose to have a technician handle it.
Is it safe to keep using my Bosch washer when dr:18 is displayed?
No, you should not continue running the washer while this code is active. The dr:18 fault indicates an uncontrolled voltage spike in the motor control system, and continued operation could cause additional damage to the motor, the control board, or other electrical components. The machine will typically refuse to complete a cycle until the fault is resolved, which is a built-in protection feature.
How much does it cost to repair a Bosch washer showing dr:18?
Repair costs depend on whether the motor control board needs replacement. A new motor control board for a Bosch washer typically costs in the range of $150 to $350 for the part alone. If you hire a technician, labor charges will add another $80 to $150 or more depending on your area. If the issue turns out to be a wiring harness problem, the repair cost can be significantly lower.
Will resetting my Bosch washer clear the dr:18 error code?
A power reset may temporarily clear the displayed code, but it will not resolve the underlying fault. Because dr:18 is caused by a hardware condition in the motor control board, the voltage spike issue will persist and the code will return once the washer attempts to run again. A proper repair requires running diagnostic test P4 and addressing the root cause, which is most commonly a faulty motor control board.

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